Explosive ammunition with fragmenting structure

ABSTRACT

The object of the invention is an explosive ammunition ( 1 ) having a fragmenting structure comprising an explosive charge ( 3 ) configured in a splinter-generating shell ( 2 ).  
     This ammunition is characterized by comprising a case ( 7 ) enclosing the shell ( 2 ) and containing means implementing a mechanical stress differential during ammunition ignition at the outer surface of the shell ( 2 ), where this differential enhances splinter generation and is distributed over a regular, 3D grid.

[0001] The technical field of the present invention is that of explosiveammunition with fragmenting shells.

[0002] In general such ammunition includes an explosive charge fittedinto a metal shell that shall generate splinters.

[0003] Splinters of a given size and shape may be generated by weakeningthe shell along a particular 3D array. Illustratively such weakening isimplemented by grooving or by local laser heating.

[0004] The French patent 2,438,686 describes ammunition of which theshell is weakened in such manner.

[0005] Moreover the French patent 2,598,214 describes how to incorporatepre-shaped splinters into the shell of an ammunition.

[0006] Such designs incur the drawback of high costs.

[0007] Such costs shall be the larger the smaller the gauge of thedesired ammunition (less than 70 mm): both machining and assembly willbe more problematical and hence more expensive.

[0008] Accordingly it is the objective of the present invention tocreate ammunition palliating said drawbacks.

[0009] As a result the ammunition of the invention allows generatingcalibrated splinters.

[0010] Therefore the objective of the present invention is explosiveammunition with a fragmenting structure receiving an explosive charge inturn received in a splinter-generating shell and characterized in thatit comprises a case enclosing the shell and being fitted with means suchthat, at ammunition initiation, they will cause a mechanical stressdifferential at the outer surface of the shell to induce splintering,said differential being regularly distributed over a 3D array.

[0011] In a first embodiment of the invention, the means causing astress differential may include an inside case surface fitted with asalient array having recessed meshes which each are bounded by a salientrib making contact with the shell, such a configuration duringammunition initiation assuring shell weakening along said ribs in orderto generate splinters.

[0012] In a second embodiment of the present invention, the meanscreating a stress differential may include a netting firmly affixed tothe case or sandwiched between the case and the shell, said nettingconstituting the weakening array.

[0013] The case may be made of plastic.

[0014] The netting may be advantageously imbedded into the case.

[0015] Further embodiment particulars may include the following:

[0016] the array may be constituted of elementary square meshes,

[0017] the shell may be made of steel or tungsten,

[0018] the case may constitute a ballistic nose cone for the ammunition.

[0019] The invention is elucidated in the following description ofdifferent modes of embodiment in relation to the attached drawings.

[0020]FIG. 1 is a diagrammatic longitudinal section of ammunition of afirst embodiment of the invention,

[0021]FIG. 2 is a cross-section of this ammunition in a plane along AAof FIG. 1,

[0022]FIG. 3 is a partial perspective of a detail of the inside surfaceof the case of this ammunition,

[0023]FIG. 4 is a schematic longitudinal section of ammunition of asecond embodiment of the present invention,

[0024]FIG. 5 is a perspective of the netting alone which shall be firmlyjoined to this ammunition's case, and

[0025]FIG. 6 is a cross-section similar to that of FIG. 2 of a variationof the first embodiment.

[0026] In FIG. 1, an explosive ammunition 1 of a first embodiment of theinvention comprises a fragmenting structure constituted by a shell 2made of steel or tungsten and bounding an inside volume receiving anexplosive charge 3.

[0027] The shell material shall be devoid of localized weakening meshes.Said material may have been thermally weakened for instance by quenchhardening.

[0028] Illustratively by crimping, the shell 2 is fixed in place bybeing crimped into the zone of a shoulder 4 a of a closing base 4 whichis fitted with a belt 12 acting as a hermetic seal inside the omittedtube of a weapon.

[0029] The base 4 contains an initiation system 5 that is well known tothe expert and therefore is not shown in detail and which will initiatethe explosive charge 3 through a detonator 6.

[0030] The ammunition of the present invention is characterized by acase 7 enclosing the shell 2. Illustratively the case 7 is fixed inplace by being glued to a second shoulder 4 b of the base 4.

[0031] This case includes means whereby a mechanical stress differentialis generated during the ammunition's explosive charge initiation at theoutside surface of the shell 2. This differential is designed in such away as to enhance the creation of splinters and it is regularlydistributed over a 3D array.

[0032] Such a stress differential is attained by configuring meansimplementing high mechanical strength at the outside surface of theshell 2, said mechanical strength being irregular across the array whichitself is regular.

[0033] Accordingly the shell fragmentation shall be oriented accordingto the array of said stress differential without the need to weakenbeforehand said shell across a fragmentation array.

[0034] In a first embodiment shown in FIGS. 1 through 3, the meanscausing a stress differential comprise an inside surface 8 of the shell7 which is fitted with an array of salients.

[0035] Each mesh 9 of this array is hollow and such a mesh is bounded bya rib 10 making contact with the shell 2.

[0036] Accordingly the case 7 makes contact with the shell 3 only by theribs 10. Such a design assures that, during ammunition initiation,weakening of the shell 3 shall take place along the ribs 10, and thatsplinters calibrated to the dimensions of the array's mesh 9 shall beformed.

[0037] In this embodiment the elementary mesh of the array of meshes issquare. Each side of this square is about 2 mm with respect to a 35 mmammunition (maximum outside diameter of the case 7). The height of themesh rib 10 is about 1 mm for a case which is 2 mm thick and is made ofa plastic such as a polyamide or a polycarbonate.

[0038] The local mass of the case 7 and its bursting strength permitdesigning the stress differential between the (hollow) center of themeshes 9 and the ribs 10. These parameters will be controlled toappropriately selecting the material and its thickness.

[0039] Advantageously a plastic of the polyamide type is selected,though this polyamide also may be filled with glass fibers. Such aselection leads to the desired stress differential while only absorbinga small proportion of the charge's explosive energy, that is, withoutdegrading ammunition performance.

[0040] The case 7 is fitted with a nose cone 7 a at its front part.

[0041] Accordingly, the ammunition of the invention offers very simplemanufacture and economy: The splinter-generating shell 2 comprisestotally smooth inner and outer surfaces. As a result, said shell 2 canbe made by sintering or forging.

[0042] After being loaded with the explosive material, the shell 2 isaffixed to the base 4 fitted with the priming system 5/6. Thereupon thecase 7 is mounted around the shell 2. The inside diameter of the case 7is selected slightly less—by a few tenths of a mm—than the outsidediameter of the shell 2. In this manner very good contact is set upbetween the mesh ribs 10 and the outer surface of the shell 2.

[0043] The case 7 is manufactured in simple and economical manner byinjecting plastic into a mold of suitable geometry. Moreover this case 7assumes the function of a nose-cone for the ammunition.

[0044] Contrary to the case of the ammunition of the prior art, thepresent invention no longer requires locally weakening or locallymachining the structure of the shell 2.

[0045] Therefore it is henceforth feasible to manufacture a tungstenshell in especially economic manner.

[0046] Indeed, in the prior art, such a material did require molding orsintering a shell structure fitted with the desired weakening array.Such a procedure was sensitive and very costly.

[0047] As regards the shell structure of the invention, on the otherhand, it is smooth and the meshwork is determined only by the geometryof the inside surface of the case 7.

[0048] In a variation of this embodiment, the inside case surface may befitted with a complementary topography, that is with a configurationwherein the meshes would contact the outer shell surface and would bebounded by grooves. However such a design would entail less efficacywith respect to the speed of the resulting splinters.

[0049] In terms of embodiment variations, it is feasible of course touse other geometries than those of said array of salients.Illustratively the elementary mesh may be diamond shaped, or hexagonal,or round.

[0050]FIG. 4 shows an ammunition 1 of a second embodiment of theinvention.

[0051] This second embodiment differs from the first by the geometry ofthe means causing a stress differential at the shell.

[0052] These means comprise a netting 11 firmly affixed to the case 7.The netting makes use of a steel wire 0.1 mm in diameter. The nettingmay be metallic or made of a high-density (>1 g/cm³) plastic, or aceramic or a glass fiber.

[0053] The netting 11 is shown by itself in FIG. 5. Such netting iscylindrical overall. It is made by winding a planar netting and weldingtogether the edges of its ribs.

[0054] In this instance the netting comprises an elementary mesh 12which is square, though it may also assume other geometries (diamond,rectangular, hexagonal, circular . . . ).

[0055] The netting 11 is imbedded in the material of the case 7. Saidcase 7 is made of a plastic injected around the netting which iscontained within the injection mold. In this manner almost the entireinner surface of the case 7 makes contact with the outer surface of theshell 2. As a result case warping during storage or transportation willbe averted.

[0056] Such an embodiment mode simplifies the geometry of the mold usedto fabricate the case 7. However it entails making a netting.

[0057] The advantage of such an embodiment is the manufacture of athinner case 7. The netting assumes the function of bracing the case 7and allows setting up the stress differential at a case thickness ofroughly 1 mm.

[0058] When employing such a manufacturing mode, it is easy to pass fromone mesh geometry to another merely by modifying the netting 11 withoutneeding to modify the injection-molding equipment for the case 7.

[0059] The stress differential may be controlled by changing thewire/filament diameter of the netting 11.

[0060] As an embodiment variation, and instead of imbedding the nettinginto the case 7, this netting can be merely positioned between the case7 and the shell 2.

[0061] Obviously the two embodiments described in relation to FIGS. 1and 4 also may be combined.

[0062] Accordingly FIG. 6 shows a cross-section of ammunition 1comprising a case 7 fitted with an inside surface comprising a raisednetting of which the hollow meshes 9 are bounded by a rib 10 in contactwith the shell 2. This case 7 also is fitted with an insert constitutedby a netting 11 of which the meshes are substantially identical withthose of the raised netting and are configured in coincidence with themeshes of this netting.

[0063] Accordingly the wires/filaments of the netting 11 are situatedopposite the ribs 10 of the netting of the case 7.

[0064] Such a design allows reinforcing the geometry of the case 7 andalso to increase the stress differential.

[0065] It may be possible to combine a netting with a netting with anarray of salients and/or mesh geometries. Such a design would allowgenerating at least two kinds of splinters of different dimensions.

1. An explosive ammunition (1) having a fragmenting structure whichcomprises an explosive charge (3) configured in a splinter-generatingshell (2), where said ammunition is characterized in that it comprises acase (7) enclosing the shell (2) and including means which duringammunition initiation will implement a mechanical stress differential atthe outside surface of the shell (2), where said differential enhancessplinter generation and which is spatially distributed across a regulararray.
 2. Explosive ammunition as claimed in claim 1, characterized inthat the means creating a stress differential include an inside surface(8) of the case (7) fitted with an array of salients of which eachrelated mesh (9) is hollow and is bounded by a salient rib (10) makingcontact with the shell (2), such a configuration assuring weakening thisshell (2) during ammunition initiation along the ribs (10) to generatesplinters.
 3. Explosive ammunition as claimed in either of claims 1 and2, characterized in that the means generating a stress differentialinclude a netting (11) solidly joined to the case (7) or placed betweenthe case and the shell (2), said netting constituting the weakeningarray.
 4. Explosive ammunition as claimed in one of claims 1 through 3,characterized in that the case (7) is made of plastic.
 5. Explosiveammunition as claimed in either of claims 3 and 4, characterized in thatthe netting (11) is imbedded in the case.
 6. Explosive ammunition asclaimed in one of claims 1 through 6, characterized in that the array isfitted with square elementary meshes (9).
 7. Explosive ammunition asclaimed in one of claims 1 through 6, characterized in that the shell(2) is made of steel or tungsten.
 8. Explosive ammunition as claimed inone of claims 1 through 7, characterized in that the case (7)constitutes a nose cone (7 a).